Ondetti et al. in U.S. Pat. No. 4,105,776 disclose that various mercaptoacyl prolines or substituted prolines, for example, where the proline ring is substituted in the 4-position by a hydroxy or lower alkyl group are useful as hypotensive agents due to their angiotensin converting enzyme inhibition activity.
Mercaptoacyl derivatives of proline wherein the acyl sidechain can be substituted by an alkyl or trifluoromethyl group and the proline can be substituted with one or more halogens are disclosed as useful hypotensive agents by Ondetti et al. in U.S. Pat. No. 4,154,935.
Mercaptoacyl derivatives of proline wherein the acyl sidechain can be substituted with a lower alkylthio group are also disclosed as useful hypotensive agents by Ondetti et al. in U.S. Pat. No. 4,116,962.
Mercaptoacyl derivatives of proline wherein the proline ring is substituted in the 3- or 4-position by an ether or thioether group are disclosed as useful hypotensive agents by Ondetti et al. in U.S. Pat. No. 126,239 filed Mar. 3, 1980.
Mercaptoacyl derivatives of 4-disubstituted prolines and 4-substituted dehydroprolines are disclosed as useful hypotensive agents by Krapcho in U.S. Ser. No. 86,905 filed Oct. 22, 1979.
Mercaptoacyl derivatives of proline substituted in the 5-position by various groups such as phenyl, hydroxyphenyl, cycloalkyl, aralkyl, etc., are disclosed as useful hypotensive agents by Iwao et al. in U.K. Patent Application No. 2,027,025.